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Chapter 5 The Physical Basis of Stress © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Overview This chapter Provides an overview of the physical basis of stress through an in-depth analysis of Selye’s general adaptation syndrome (GAS) Describes how the GAS responds to immediate and longer-term threats Ends with a critical analysis of Selye’s work based on recent studies © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Outline Overview of the major body systems involved in the stress response Fight-or-flight: An alarm reaction Resistance: A chronic, long-term stress response The physiology of exhaustion A critical look at general adaptation syndrome (GAS) © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Major Body Systems Involved in the Stress Response Communication, control, and integration The endocrine system The nervous system © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Other Major Body Systems Involved in the Stress Response Transportation and defense Cardiovascular (circulatory) system Immune system © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Other Major Body Systems Involved in the Stress Response Support and Movement Muscular system Respiration, Nutrition, and Excretion Gas exchange: The respiratory system Nutrition and excretion: The digestive system © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images The Nervous System and Fight-orFlight (An Alarm Reation) Fight-or-flight stress response helps us get out of harm’s way Selye’s General Adaptation Syndrome (GAS) alarm phase Stress response: a series of phases that continue to exact a toll on our bodies until we remove or cope with the stressor that initiates is © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Axes and Pathways Everly and Lating use these terms to describe the routes traveled through the body after a potential stressor is appraised as threatening Three different pathways The neural axis The neuroendocrine axis (a.k.a. the sympathoadrenomedullary system, or SAM) The endocrine axis (contains the hypothalamicpituitary-adrenal-cortical system, or HPAC) The axes expand on Selye’s work © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images The Neural Axis The central nervous system: brain and spinal column The peripheral nervous system: all the other nerve pathways © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Fight-or-Flight: The Brain The fight-or-flight response Originates with the brain’s perception of threat Different parts of the brain are involved in the stress response The cerebral cortex—covers the cerebrum and controls higher thought processes The diencephalon—forms the central brain core and receives and routes messages © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Fight-or-Flight: The Brain (continued) The limbic system Links the emotional brain with the thinking, rational brain The brain stem Produces autonomic functions (necessary for survival) Is pathway for both general and specific cortical arousal through the reticular activating system (RAS) © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Fight-or-Flight: The Spinal Cord The lifeline between the brain and the rest of the body © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Fight-or-Flight: The Peripheral Nervous System The somatic nervous system Transmits messages under our conscious control The autonomic nervous system Controls functions that are unconscious Sympathetic branch: activates stress responses Parasympathetic branch: deactivates stress responses (activates relaxation responses) © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Fight-or-Flight: The Endocrine System of the Neuroendocrine Axis Produces hormones associated with alarm Adrenal glands play the most significant role in the stress response Epinephrine (adrenaline) Norepinephrine (noradrenaline) © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Resistance: A Continuous, LongTerm Stress Response The physiology of resistance: The body not at rest but also not in the throes of alarm Roles played by The brain: the cerebral cortex, diencephalon, limbic system, and brain stem The endocrine axes: adrenocortical, somatotropic, thyroid, and pituitary systems © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Resistance—The Cerebral Cortex The cerebral cortex—the key part of the brain involved in resistance Our thoughts about stressors, especially illogical thoughts, keep them alive or allow them to dissipate © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Resistance—The Limbic System Interacts with the cortex as our emotions interact with our thoughts Prolongs or reduces the stress response © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Resistance—The Endocrine System The pituitary is known as the master gland All activities are orchestrated by the pituitary gland through the hypothalamus © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Resistance—The Adrenal Function The medulla secretes two key groups of hormones Gluccocorticoids (sugars) Cortisol provides energy, reduces inflammation, prolongs stress response Mineralocorticoids (salts) Aldosterone keeps blood pressure elevated © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images The Physiology of Exhaustion Selye believed all living things have a finite amount of energy to adapt to stress When that is used up, one suffers exhaustion Organisms vary in how they become exhausted © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Exhaustion—The Weak Link Selye asserted all living things have a “weak link,” the first part to fail Chronic stress puts a heavy demand on strategic body parts Heart, blood vessels, and adrenal and thyroid glands are most susceptible © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images General Adaptation Syndrome (GAS) (A Review) Developed by Selye, GAS has three distinguishable phases Alarm Resistance Exhaustion © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images A Critical Look at GAS Two major challenges in recent years Nonspecificity—Goldstein Identified different responses to seven specific stressors: water deprivation, salt deprivation, posture changes, eating a large meal, exercise, hemorrhage, and temperature alteration Eustress—Mason and Frankenhauser Found body response to threat different from body response to challenge © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images Chapter 5: The Physical Basis of Stress Summary © 2007 McGraw-Hill Higher Education. All rights reserved. Akira Kaede/Getty Images